1. Field of the Invention
The present invention relates to an aqueous dispersion for chemical/mechanical polishing.
2. Description of Background Art
The storage capacity of memory devices has remarkably increased with the increase in the degree of integration, multilayer wiring, and the like of semiconductor devices. This is supported by the progress in microfabrication technologies. However, there are problems such as an increased chip size in spite of using multilayer wiring and the like and an increased cost for production of chips because of an increased number of production steps due to the progress in microfabrication technologies. In this situation, a chemical/mechanical polishing technology has been introduced into the polishing step of processed films and the like in manufacturing semiconductor devices. The technology has attracted attention. Many microfabrication technologies such as flattening have been put into practice by applying the chemical/mechanical polishing technology.
A shallow trench isolation (STI) technology is known as such a microfabrication technology, for example (see Japanese Patent Application Laid-open No. 8-22970, for example). Various aqueous dispersions for chemical/mechanical polishing used for the microfabrication technology have been proposed. To improve polishing performance of such aqueous dispersions, organic additives are frequently added. The organic additives, however, easily rot the aqueous dispersions. To avoid this problem, a component that can make the aqueous dispersion strongly acidic or strongly alkaline, or can suppress rotting of the aqueous dispersions is added. Japanese Patent Application Laid-open No. 2002-45681, for example, discloses a method of adding hydrogen peroxide and the like to suppress the rotting. Japanese Patent Application Laid-open No. 3-197575 discloses a method of adding tetraalkylammonium chloride, tetraalkylammonium hydroxide, or the like to an aqueous dispersion containing colloidal silica as a bactericidal agent.
However, since aqueous dispersions for chemical/mechanical polishing containing ceria particles which are frequently employed in the STI technology are usually used in a neutral pH region, there is a limitation to suppression of rotting by adjusting pH. In addition, since the effect of hydrogen peroxide as an antiseptic agent does not last long, rotting may begin in an aqueous dispersion feeding device in the continuous use for about one week. If a conventionally known antiseptic agent is added to such an aqueous dispersion, the polished surface may be damaged by scratches and dishing, even if an antiseptic effect is exhibited.
The present invention has been completed to solve the above problem and has an object of providing an aqueous dispersion for chemical/mechanical polishing which does not rot even if used in a neutral pH region, produces almost no damages such as scratches and dishing on the polished surface, and can sufficiently flatten the surface.